On Tue, Apr 15, 2025 at 04:16:28PM -0700, Davidlohr Bueso wrote:
> Hello,
>
> This is a respin of the series[0] to address the sleep in atomic scenarios for
> noref migration with large folios, introduced in:
>
> 3c20917120ce61 ("block/bdev: enable large folio support for large logical block sizes")
Please resend based on vfs.fixes.
> The main difference is that it removes the first patch and moves the fix (reducing
> the i_private_lock critical region in the migration path) to the final patch, which
> also introduces the new BH_Migrate flag. It also simplifies the locking scheme in
> patch 1 to avoid folio trylocking in the atomic lookup cases. So essentially blocking
> users will take the folio lock and hence wait for migration, and otherwise nonblocking
> callers will bail the lookup if a noref migration is on-going. Blocking callers
> will also benefit from potential performance gains by reducing contention on the
> spinlock for bdev mappings.
>
> It is noteworthy that this series is probably too big for Linus' tree, so there are
> two options:
>
> 1. Revert 3c20917120ce61, add this series + 3c20917120ce61 for next. Or,
> 2. Cherry pick patch 7 as a fix for Linus' tree, and leave the rest for next.
> But that could break lookup callers that have been deemed unfit to bail.
>
> Patch 1: carves a path for callers that can block to take the folio lock.
> Patch 2: adds sleeping flavors to pagecache lookups, no users.
> Patches 3-6: converts to the new call, where possible.
> Patch 7: does the actual sleep in atomic fix.
>
> Thanks!
>
> [0] https://lore.kernel.org/all/20250410014945.2140781-1-mcgrof@xxxxxxxxxx/
>
> Davidlohr Bueso (7):
> fs/buffer: split locking for pagecache lookups
> fs/buffer: introduce sleeping flavors for pagecache lookups
> fs/buffer: use sleeping version of __find_get_block()
> fs/ocfs2: use sleeping version of __find_get_block()
> fs/jbd2: use sleeping version of __find_get_block()
> fs/ext4: use sleeping version of sb_find_get_block()
> mm/migrate: fix sleep in atomic for large folios and buffer heads
>
> fs/buffer.c | 73 +++++++++++++++++++++++++++----------
> fs/ext4/ialloc.c | 3 +-
> fs/ext4/mballoc.c | 3 +-
> fs/jbd2/revoke.c | 15 +++++---
> fs/ocfs2/journal.c | 2 +-
> include/linux/buffer_head.h | 9 +++++
> mm/migrate.c | 8 ++--
> 7 files changed, 82 insertions(+), 31 deletions(-)
>
> --
> 2.39.5
>
